The present invention relates to a receiver of a multiple subsample transmission signal having a freeze function.
A "MUSE system" has been proposed as one of the methods for compressing a band of a wideband video signal such as a high grade television signal. Full particulars thereof are given in, for example, NHK Technical Bulletin "Development FOR THE MUSE system" vol. 39, No. 2 1987. In this MUSE system, a video signal is subjected to offset sampling between fields, frames and lines, and the band is compressed through the processing in which a sampling phase makes a round in four fields. Therefore, in the receiver, transmitted video signals that are transmitted in consecutive order over four fields are stored by providing a frame memory, and these are composed thereby to restore to an original high grade television signal. A related art of a television receiver of the MUSE system will be described with reference to FIG. 1.
A digitized video signal is supplied to a signal input terminal 10. In a still picture processing circuit 11, after conducting interpolation between frames using the frame memory, interpolation between fields is conducted so as to restore a still picture image and to send it out to a mixing circuit 14. On the other hand, in a moving picture processing circuit 12, field interpolation is conducted so as to restore a moving picture image and to send it out to the mixing circuit 14. A movement detecting circuit 13 detects a moving portion by using frame correlation of the video signals, and supplies a movement control signal to the mixing circuit 14. In the mixing circuit 14, an output signal of the still picture processing circuit 11 and an output signal of the moving picture processing circuit 12 are mixed with each other at a predetermined ratio in a picture element unit corresponding to the movement control signal so as to conduct restoration. The output signal of the mixing circuit 14 is restored to such a picture quality that is suited to be put to practical use, but processing in the time base direction is performed in a temporal circuit 15 in order to restore it further completely. The temporal circuit 15 is composed of a temporal arithmetic circuit 16 and a frame memory 17. A low-frequency band component of the output signal of the mixing circuit 14 is separated by a two-dimensional space filter in the temporal arithmetic circuit 16, and a high-frequency band component is subjected to band limit in the time base direction by a temporal low-pass filter composed of the temporal arithmetic circuit 16 and the frame memory 17, and composed with the original low-frequency band component thereafter in the temporal arithmetic circuit 16, thus obtaining a restored high grade television signal at an output terminal 18.
In such a receiver as described above, however, there has been a problem that it is impossible to display any display scope under a still state, that is, to perform so-called freeze display.